Method for separating monochlorocarboxylic acids from dichlorocarboxylic acids



United States Patent CARBOXYLIC ACIDS FROM DICHLOROCAR- BOXYLIC ACIDS Robert E. Anderson, Midland, Mich., assignor to The Dow Chemical Company, Midland, Mich., a corporation of elaware No Drawing. Filed Jan. 24, 1966, Ser. No. 522,370

7 Claims. (Cl.

This invention concerns the separation of a dichlorocarboxylic acid having the formula CI RCO' H, wherein R is -CH- or CHCH from an analogous monopresence of a separatory component such as sulfurous acid.

In the preparation of monochloroacetic acid and dichloroacetic acid, hereinafter MCAA and DCAA, respectively, and monochloropropionic acid and dichloropropionic acid, hereinafter MCPA and DCPA, respectively, there each of the product tion or crystallization.

In the process of this invention, the loading of the chlorocarboxylic acids far exceeds the normal operating capacity of the By weak base anion exchange resins is meant those anion exchange resins which have -NR -NRH and NH functionality, i.e., are in the base form. They and polyalkylene polyamines. The hydrocarbonyl portion of the amine may be aliphatic, aromatic, cycloaliphatic, araliphatic and alkaromatic. Such resins and their method of preparation are disclosed in US. Patents 2,356,151; 2,366,008; 2,591,573; and 2,597,439. Epichlorohydrin-ammonia and epichlorohy- 3,409,667 Patented Nov. 5, 1968 drin-amine anion exchange condensation polymers where- 'n amine has the operation a columnar form of the water-swollen particulate resin is used.

Sulfurous acid in concentrated form and advantageousadded as separatory aids can advantageously be used, in amounts up to saturation, i.e., if they have an ionization constant (afiinity) for the weakly basic resins between those of the chlorocarboxylic acids to be separated, e.g., o nitrobenzoic acid, 2 methyl 6 nitrobenzoic acid, and phosphoric acid.

Any strong non-oxidizing mineral acid, e.g., sulfuric, phosphoric or hydrochloric that it is chemically inert to the system, and can be removed from the chlorocarboxylic acid products by distillation.

In practice, there is added to an aqueous solution of monochloroand dichlorocarboxylic acids concentrated sulfurous acid, preferably as sulfur dioxide up to saturation of said solution. there can be added separated. Such resulting solution is then fed to a column of water-swollen particulate ion exchange resin in the base form, advantageously to maxicarbonate or phosphate, which is water-soluble, and thereafter rinsed with water, advantageously deionized (DI) or distilled Water to neutrality of the elfiuent.

The following examples describe completely representative specific embodiments and the best mode contemplated by the inventor for They are not to be considered as limiting process other than as claimed.

EXAMPLE I A quantity of ml. of water-swollen 50-100 U.S. base form (polymeric hydrochloric acid. The acid breakvolume of 340 ml., indicating an ca. 3 me./ml. resin. The column was exhausted with N through occurred at a A quantity of 250 ml. mixed acid feed having an analysis of 0.48 N MCAA 0.50 N DCAA 0.32 N sulfurous acid TABLE I Normality Vol. of Efiluent,

ml. MCAA HzS Os DCAA HCl 50 655 005 0 I00 1. 285 029 0 0 I50 533 677 06 002 200 096 195 927 117 250 0 012 757 557 300 0 012 312 863 350 O 0 12 640 400 0 0 028 22 450 0 0 016 14 a very good separation. are used to (2) Chloride ion concentration was determined by potentiometric titration with N/ AgNO chlorine was determined by potentiometric hydrolyzed sample with N/10 AgNOg.

N Total 01 N Hcr'r O1AcOH+ ClgAcOH The hydrolysis was carried out by placing a 2 ml. sample, 10-15 ml. of water and half a dozen NaOH pellets in a small flask and heating at mild reflux. Chloroacetic acid was found to be completely hydrolyzed under these conditions after two hours, but dichloroacetic acid required considerably longer. All samples were run at least 8 hours and preferably overnight.

(4) One sa ple was titrated and another after heating on a hot plate until there was no odor of S0 The dilference in these two titrations was taken as an indication of the concentration of H 50 present.

(3) Total titration of a for hydrogen ion directly,

EXAMPLE II A commercial mixture of MCPA was diluted with water and S0 was bubbled through to saturation. The procedure of Example I Was then repeated using the same procedure and the same column of resin after regeneration. The composition of the feed follows:

0.34 N MCPA 0.67 N DCPA 0.87 N H 50 of the MCPA was recovered free of the DCAA and in an average concentration of about 4%. The rest of the ml. fractions and MCPA was in the DCPA product. Approximately 87% 'of the DCPA was recovered as ca. a 5% solution containing ca. 0.3% MCPA. The rest of the DCPA was sorbed on the resin and could be eluted as an increasingly dilute, less than 1%, solution. Multiple cycles and narrower effluent fractions are used to obtain product streams of higher purity.

EXAMPLE III Beds of ml. of base chlorohydrin-ammonia resin for-m Dowex 4 resin, an epihaving a wet bed capacity of ca. 2 meq./ml. in strong acid; Duolite A30B resin, an epichlorohydrin-polyamine resin having a wet bed capacity of ca. 2.6 meq./ml. in strong acid; and Amberlite IR-4B resin, a polyphenolformaldehyde resin with polyamine functionality, having a wet bed capacity of 2.5 meq./ ml. in strong acid, respectively; were each loaded with 150 ml. of a feed having the following composition;

.583 N MCAA .583 N DCAA .35 N H SO With III-4B, HQSOS normality, 0.27. followed by elution with 400 ml. of N hydrochloric acid and then with DI water. The acid breakthrough on the resins listed was ml., 248 ml. and 377 ml., respectively. The flow rates varied from 0.4 to 0.7 gal./min./ft. except for Amberlite IR-4B resin which almost stopped flowing just before the acid breakthrough. By adding more head to its column, the IR+4B resin flow rate was increased to 0.5 gal./min./ft. before it decreased gradually down to 0.2 gal./min./ft. The acid breakthrough in the efiiuent of these resins was the zero point for volume of efliuent in the following Tables II, III and IV. The normality of each component was listed in the fraction where it appeared.

TABLE II.-SEPARATION OF CHLOROACETIC AND DI- CHLORACETIO ACID ON DOWEX 4 RESIN BY ELUIING WITH N/l 1101 AND DI H O Ml. in Fraction Normality of Components MCAA DCAA H01 Fraction No.

Total ml.

Total Acid IIzSOg H2803 recovery, 97.8%. MCAA recovery, 91.4%. DCAA recovery, 98.5%.

OF CHLORACETIC AND DI ON DUOLITE A303 BY ELUTING CHLOROACETIC ACID WITH N/l H01 AND DI H20 Frac- Ml. in Normality of Components tion Frac- No. tion BLE III.SEPARATION H280; recovery, 95.7%. MCAA recovery, 96.9%. DCAA recovery, 103%.

anion exchange resin which resin sorbs said chlorohihR Xfi f 3N ffi fiiiiifi rtthh 1 5% b 1- -d car oxy 1c aci s, ELUTING WITH N/l HO] (3) eluting said chlorocarboxylic acids with a strong t Total ljormality gp e mineral acid eluant in fractions, the earlier frac- No, tion m1, H2503 MCAA DCAA H01 Total 5 tions of which are predominantly those of the mono- Acid chlorocarboxy lic acid and the later fractions of 50 50 which are predominantly those of the dichlorocar- 23 23 is boxyllc acid and recovering product chlorocar- 50 200 13 boxylic acids therefrom. 28 338 i-gg l 2. Method of claim 1 wherein the process is repeated '5 1 1:005 for a plurality of cycles to give product chlorocarboxylic gg 5 83 5 1 8 acids of a predetermined purity. 55 555 95 11018 3. The method of claim 1 wherein the mixture is that 88 98g :gg {83 of monochloroacetic and dichloroacetioacid. No DI water was used after 400 m1 of N/l H01 as in the Dreviou l5 4. Method of'clalm 1 whfarem the m'lxtilre 1S that of runs because it was thought that it woilld swell the resin and stop the monochloroproplomc and dlchloroproplomc acld flow altogether. 5 Method of claim 1 wherein the solution is saturated fi ggyfggggg ggg wlth sulfurous acid by adding sulfur dioxide thereto DOAA recovery, 98.9%. 6 A method for separating from aqueous solution a mixture of monochloroand dichloroacetic acid which comprises The substitution in each of Examples 1-111 of another 1 saturating said solution i h lf r dioxide, acid as a separatory aid 1n place of sulfurous acid, which 2 f di said solution to a column f a weak b acid separatory aid has an ionization constant or a first anion exchange resin in the base f hi resin ionization constant intermediate those of the chloro- Serbs said chloroacetic acids carboxyllc acids P separated, such as Phosphoric (3) eluting said chloroacetic acids in fractions with acld: o'mtrobenzolc acld and 2 methyl 6 obenzolc concentrated hydrochloric acid, the earlier eluate acid, gives similar advantageous results It is not critical fractions f which are predominantly those f that the aqueous solution of chlorocarboxylic acids be monochloroacetic i and the latelehtate t saturated with the acid separatory aid It is, however, tions of which are predominantly those f dichloropreferred that the aqueous solutron of chlorocarboxylic acetic acid and recovering product mohochloroacetic acids to be separated be saturated w1th the acid sepand dichlomacetic acids th f om aratory aid, since better separations of the product acids Method of claim 6 wherein the process i tepaated are Obtained Howevert any amount acld for a plurality of cycles to give product chlorocarboxylic aratory aid less than saturation concentration is operaacids of predetermined purity ble 1n affecting an improved separation of product chlorocarboxylic acids. References Cited I claim: 1. A method of separating from aqueous solution a UNITED STATES PATENTS mixture of analogous monochloroand dichlorocar- 3,272,737 9/ 1966 Hansen et 260539 XR boxylic acids having two to three carbon atoms which comprises (1) adding to said solution an acid separatory aid having an ionization constant or a first ionization constant intermediate those of the two chlorocarboxylic 4 acids, (2) feeding said solution to a column of a weak base OTHER REFERENCES Funasaka et al., Bunseki Kagaku, vol. 7, pp. 69-73 (1958).

LORRAINE A. WEINBERGER, Primary Examiner. A. P. HALLUIN, Assistant Examiner. 

1. A METHOD OF SEPARATING FROM AQUEOUS SOLUTION A MIXTURE OF ANALOGOUS MONOCHLORO- AND DICHLOROCARBOXYLIC ACIDS HAVING TWO OR THREE CARBON ATOMS WHICH COMPRISES (1) ADDING TO SAID SOLUTION AN ACID SEPARATORY AID HAVING AN IONIZATION CONSTANT OR A FIRST IONIZATION CONSTANT INTERMEDIATE THOSE OF THE TWO CHLOROCARBOXYLIC ACIDS, (2) FEEDING SAID SOLUTION TO A COLUMN OF A WEAK BASE ANION EXCHANGE RESIN WHICH RESIN SORBS SAID CHLOROCARBOXYLIC ACIDS, (3) ELUTING SAID CHLOROCARBOXYLIC ACIDS WITH A STRONG MINERAL ACID ELUANT IN FRACTIONS, THE EARLIER FRACTIONS OF WHICH ARE PREDOMINANTLY THOSE OF THE MONOCHLOROCARBOYXLIC ACID AND THE LATER FRACTIONS OF WHICH ARE PREDOMINANTLY THOSE OF THE DICHLOROCARBOXYLIC ACID AND RECOVERING PRODUCT CHLOROCARBOXYLIC ACIDS THEREFROM. 